Disposable absorbent articles, such as diapers, pull-on diapers, training pants, adult incontinence pads, wipes, facial tissue, toilet tissue, napkins, paper towels and the like are often manufactured and/or packaged on a high-speed production line where individual articles may move along a production path at a speed of hundreds of meters per minute. During the manufacturing and/or packaging process the disposable absorbent articles may undergo a folding process. For example, a disposable diaper may undergo a bifolding process prior to being placed in a package. In a bifolding process, an article is folded into two parts. The article may be folded in half in the longitudinal direction such that two opposing portions of the article are brought together in a face-to-face configuration. Some manufacturers of disposable diapers may provide a bifolded diaper that has a front end edge that is substantially aligned with a back end edge of the diaper. However, current manufacturing practices often do not provide the desired degree of alignment between the diaper end edges, resulting in a diaper that may have undesirable characteristics in the marketplace. The problem may be further compounded for so-called “training pant” diapers which, after being folded into a U in the same or similar way as conventional diapers, are joined permanently, e.g., sealed, along the lateral portions to form a closed annular girdle enabling the diaper to be used pant-fashion. The high degree of precision for folding training pants may require increased accuracy beyond that of a traditional taped diaper, so that the lateral portions of the training pant, which are to be joined permanently, are configured with the desired overlap.
In some processes for providing a folded absorbent article, a portion of a production line for making absorbent articles may include a primary roll for carrying the absorbent article. The primary roll may apply a suction force, e.g. vacuum, to hold the absorbent article in the proper position during the folding process. Such processes may also utilize one or more secondary rolls for pulling a portion of the absorbent article, typically the leading end portion, off of the primary roll. The secondary roll(s) may employ vacuum pressure to pull the leading portion of the absorbent article off of the primary roll and hold the pulled off portion to the secondary roll surface of the second roll. As the manufacturing process or converting operation continues, more of the leading end portion of the article may continue to be pulled off of the primary roll and attached to the secondary roll. Next, the article may be subjected to forces that pull the leading and trailing end portions of the article in substantially opposite directions. For example, clips or other mechanical holding means may be used to hold the middle portion of the absorbent article to the surface of the primary roll in order to provide sufficient force to pull the leading end portion of the article from of the secondary roll. Typically, once the leading end portion of the article is pulled from or released by the secondary roll, the leading end portion will travel back toward the primary roll to continue through the folding process. However, when the leading end portion of the article is pulled/released from the secondary roll, it may be subjected to turbulence or other forces that cause the leading end portion to move about in an uncontrolled manner, potentially resulting in a folded article with undesirably misaligned end and/or side edges.
In order to overcome the problems associated with the uncontrolled movement of the leading end portion when the leading end portion is separated from the secondary roll, processes may utilize a transfer roll or conveyor configured with a vacuum system to receive the leading end portion of the absorbent article and transfer it back to the primary roll. In some instances, the surface of the transfer roll or conveyor includes a porous belt or other foraminous surface that allows the suction force of the vacuum system to be exerted at the surface of the conveyor or roll. The surface speed of the transfer conveyor or roll may be constant, and in some instances is set to match the surface speed of the primary roll. In this way, the leading end portion of the article can be transferred back to the primary roll at about the same speed as the trailing end portion is travelling, potentially reducing the chance for misalignment of the leading and trailing end portions during folding. However, when the leading end portion of the article is separated from the secondary roll, the relative speeds of the leading end portion and the surface of the transfer conveyor or roll may still be substantially different. While the transfer roll or conveyor may be able to capture the leading end portion and hold it to the conveyor or roll surface with vacuum pressure and thereby minimize uncontrolled movement, the leading end portion may still end up in an undesirable configuration (e.g., wrinkled, bunched, crooked, etc.) due to the rapid acceleration typically experienced by the leading edge when it contacts the continuously moving transfer roll or conveyor.
In further efforts to overcome the problems resulting from the rapid acceleration of the leading end portion of the absorbent article when contacting the transfer roll or conveyor, some processes may utilize a transfer roll or conveyor that decelerates the transfer roll or conveyor to substantially match the speed of the leading end portion of the absorbent article when transferring the leading portion from the secondary roll to the transfer roll or conveyor. Once the leading end portion is transferred to the transfer roll or conveyor, the transfer roll or conveyor is accelerated to substantially match the speed of the primary roll. However, before the leading end portion of the article is pulled/released from the secondary roll rotating at a constant speed, the outer surface of the rotating secondary roll will move relative to or slip under leading end portion of the article. Frictional forces resulting from the relative movement or slippage between the leading end portion of the article can cause in undesirable resulting configurations. For example, leading end portions of articles with laterally extending components, such as diaper ears or fasteners, may become wrinkled or crooked.